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Resolving Trophodynamic Consequences of Climate Change (RECONN2): Match-mismatch between Secondary and Tertiary Production in the Baltic Sea

Subject Area Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Term from 2004 to 2011
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 5430034
 
Final Report Year 2012

Final Report Abstract

The project RECONN2 within the priority program 1162 AQUASHIFT was proposed to improve our capabilities of understanding and predicting climate change impacts on a marine ecosystem, here the Baltic Sea. The proposed research project (RECONN2) was designed to specifically address the effects of a potential rise in ambient temperature on the matchmismatch dynamics of zooplankton, larval and adult fish in the Baltic Sea. The key trophic player in focus was sprat (Sprattus sprattus), a small clupeid fish species that is a sensitive bio-indicator of climate change. Further, sprat is an ecological and economical important species as well in the Baltic as in the North Sea. However, problems occurred in successfully rearing sprat larvae during the project and a number of relevant experiments concerning larval growth were performed with herring larvae. During the first funding period, we focussed on the implications of rising ambient temperatures on vital rates (survival rates, growth and development) of early life stages of Baltic clupeids by applying a combination of experimental and field data approaches (time series analyses). Further, temperature dependent growth models for clupeid fish larvae were established taking into account RNA/DNA ratios. During the second phase, the aforementioned experiments were complemented by conducting a series of experimental trials that focused on the influence of differences in salinity and food size spectrum on development, growth and survival of fish eggs and larvae. Additionally, the research focus during the second phase was to develop a more general picture of the influence of climatic processes on Baltic sprat population dynamics. This included (i) developing process models on adult sprat growth and reproduction based on available field data, and (ii) combining experimental data, field data as well as modelling activities (in co-operation with RECONN 1). For the synthesis of RECONN2 a life table approach was chosen. This approach required a complete parameterisation of life stage dependent sprat vital rates to establish a population matrix model. The life table approach provided a single model framework that allows us (i) to identify critical life stages of sprat in relation to population dynamics and different temperature scenarios, (ii) to simulate the future population development under different climate change scenarios, and (iii) to draw conclusions on population dynamics in a matchmismatch context. The main results were that the transition probability of feeding larvae has the largest impact on population dynamic and a temperature elevation up to 4°C would lead to an increase in the intrinsic growth rate of the modelled sprat population. The latter result is due to the fact, that development and stage duration of sprat early life stages is accelerated by increasing ambient temperatures. However, feeding larvae will only profit from accelerated development when quantity and quality of their prey items allows maintaining the higher metabolism. Thus, an elevation in temperature will narrow the “window of opportunity” beyond a certain level, because the necessity to find a perfect match situation becomes more important. Within RECONN2 we have identified aspects of the thermal ecology of Baltic sprat that require future study such as the potential importance of YOY overwinter survival and feedback loops between temperature, prey and sprat reproduction.

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